Algorithm 1: ML estimator.

Initialization            Pre-calculation of $\Psi \leftarrow {\Omega }^{-1}$            Creation of pilot sequence c and vector y of observables       Computation            Auxiliary terms: $M_{cc}\leftarrow c^T\Psi c, M_{cy}\leftarrow y^T\Psi c, M_{yy}\leftarrow y^T\Psi y$            Channel gain estimate: $\widehat{A}\leftarrow \frac{M_{cy}}{M_{cc}}$            Noise power estimate: ${\widehat{P}}_n\leftarrow \frac{1}{4(1+\alpha )L}\left(M_{yy}-\frac{M_{cy}^2}{M_{cc}}\right)$       Output            SNR estimate: ${\widehat{\rho }}_s\leftarrow \frac{{\widehat{A}}^2}{{\widehat{P}}_n}$